Progress bar: WordPress AJAX and HTTP Headers (ERR_RESPONSE_HEADERS_TOO_BIG)

This is a quick note that explains a gotcha with regards to creating a progress bar or similar.  I’m writing code for WordPress but this strongly related to PHP, SESSION, AJAX and web browsers.

I wanted to use _SESSION to record progress in a loop which in concept looks like:

 foreach ($json['rows'] as $computer) {

I had read that parallel AJAX calls might fail if used with PHP’s _SESSION because sessions block.  I thought storing the same information in a database would use a lot of resource which I want to avoid and so I thought I might be able free the block.  The code became:

 foreach ($json['rows'] as $division) {

This was working great for a short loop but fails against longer loops.  Firefox was returning: xhr.status 0 which meant that my AJAX call would not finish and cancel the timer firing the progress check.  When you search for “ajax xhr.status 0” some reasonable fixes come up.  I think my code is better because of them but they didn’t fix this error.

When I ran this under Chrome I ran in to the same issue but the Javascript console kicked up: net::ERR_RESPONSE_HEADERS_TOO_BIG and bingo! had something else to chase.  In my Docker container running a LAMP stack with WordPress, I ran ngrep in order to see what headers were being sent and the culprit was there loud and proud:

..Set-Cookie: PHPSESSID=2292e08a375041bc1d32c1432d3d66c7; path=/..Set-Cookie: PHPSESSID=2292e08a375041bc1d32c1432d3d66c7; path=/..Set-Cookie: PHPSESSID=2292e08a375041bc1d32c1432d3d66c7; pat
 h=/..Set-Cookie: PHPSESSID=2292e08a375041bc1d32c1432d3d66c7; path=/..Set-Cookie: PHPSESSID=2292e08a375041bc1d32c1432d3d66c7; path=/..Set-Cookie: PHPSESSID=2292e08a375041bc1d32c1432d3d66c7; 
 path=/..Set-Cookie: PHPSESSID=2292e08a375041bc1d32c1432d3d66c7; path=/..Set-Cookie: PHPSESSID=2292e08a375041bc1d32c1432d3d66c7; path=/..Set-Cookie: PHPSESSID=2292e08a375041bc1d32c1432d3d66c
 7; path=/..Set-Cookie: PHPSESSID=2292e08a375041bc1d32c1432d3d66c7; path=/..Set-Cookie: PHPSESSID=2292e08a375041bc1d32c1432d3d66c7; path=/..Set-Cookie: PHPSESSID=2292e08a375041bc1d32c1432d3d
 66c7; path=/..Set-Cookie: PHPSESSID=2292e08a375041bc1d32c1432d3d66c7; path=/..Set-Cookie: PHPSESSID=2292e08a375041bc1d32c1432d3d66c7; path=/..Set-Cookie: PHPSESSID=2292e08a375041bc1d32c1432
 d3d66c7; path=/..Set-Cookie: PHPSESSID=2292e08a375041bc1d32c1432d3d66c7; path=/..Set-Cookie: PHPSESSID=2292e08a375041bc1d32c1432d3d66c7; path=/..Set-Cookie: PHPSESSID=2292e08a375041bc1d32c1
 432d3d66c7; path=/..Set-Cookie: PHPSESSID=2292e08a375041bc1d32c1432d3d66c7; path=/..Set-Cookie: PHPSESSID=2292e08a375041bc1d32c1432d3d66c7; path=/..Set-Cookie: PHPSESSID=2292e08a375041bc1d3
 2c1432d3d66c7; path=/..Set-Cookie: PHPSESSID=2292e08a375041bc1d32c1432d3d66c7; path=/..Set-Cookie: PHPSESSID=2292e08a375041bc1d32c1432d3d66c7; path=/..Set-Cookie: PHPSESSID=2292e08a375041bc
 1d32c1432d3d66c7; path=/..Set-Cookie: PHPSESSID=2292e08a375041bc1d32c1432d3d66c7; path=/..Set-Cookie: PHPSESSID=2292e08a375041bc1d32c1432d3d66c7; path=/..Set-Cookie: PHPSESSID=2292e08a37504
 1bc1d32c1432d3d66c7; path=/..Set-Cookie: PHPSESSID=2292e08a375041bc1d32c1432d3d66c7; path=/..Set-Cookie: PHPSESSID=2292e08a375041bc1d32c1432d3d66c7; path=/..Set-Cookie: PHPSESSID=2292e08a37
 5041bc1d32c1432d3d66c7; path=/..Set-Cookie: PHPSESSID=2292e08a375041bc1d32c1432d3d66c7;

Every time a session_start() is called a cookie is written to the output.  I thought I was defeated and a database solution was the proper route (it may still be…).  However, I found header_remove(‘Set-Cookie’); which if called before EVERY session_start(); it strips the “Set-Cookie” pragmas from the header.  The code now looks a bit like this:

 foreach ($json['rows'] as $computer) {

I hope this helps you so that you don’t have to bruise your head against a wall like I did.


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Docker Composer and Developing Plugins for WordPress


I am developing a WordPress plugin from scratch.  Rather than hacking on someone else’s plugin I will be going through lots of iterations as I develop a robust and reusable framework.  I have recently been using Docker containers to speed up the creation of environments separated from the other 24 years of open source dev and GNU/Linux administrative entropy on my PC.

I started this time by looking for a container that supports WordPress.  I was looking for a container that had WordPress, Apache and MySQL neatly wrapped and configured to save me time (see DevOps.) Luckily, I happened across a post which describes how to do this with Docker Composer.

By adjusting the recipe, I have been able to create the containers but preserve the plugin code outside them.  This means I can tear down and build up the containers quickly.  This helps a developer because a fresh database can be tested against over and over using:

docker-compose up -d
docker-compose down --volume

Here is the recipe for an environment that allows a developer to create a plugin for WordPress from scratch:

In a directory like ‘docker-myproject’  create docker-compose.yml:

version: '3'

 image: mysql:5.7
 - db_data:/var/lib/mysql
 restart: always
 MYSQL_DATABASE: wordpress
 MYSQL_USER: wordpress
 MYSQL_PASSWORD: wordpress

 - db
 image: wordpress:latest
 - /usr1/home/me/Dev/docker-myproject/plugins:/var/www/html/wp-content/plugins
 - ""
 restart: always

The twist is the first volume mapping from my desktop into the WordPress file structure.  I can use all the tools I like to use outside of the pristine configuration inside the containers.  When I need to test the installation/activation of the plugin I can delete the containers and rebuild them.  The plugin code is not touched and I have a clean database to test against.  A lovely little thing.

Well done you.


Posted in Development, Docker, Linux SysAdmin | Tagged , , , | Leave a comment

Using Fail2Ban to protect your LAMP application

From the Fail2Ban Homepage:

Fail2ban scans log files (e.g. /var/log/apache/error_log) and bans IPs that show the  malicious signs — too many password failures, seeking for exploits, etc. Generally Fail2Ban is then used to update firewall rules to reject the IP addresses for a specified amount of time, although any arbitrary other action (e.g. sending an email) could also be configured. Out of the box Fail2Ban comes with filters for various services (apache, courier, ssh, etc).

The Problem

When a web site comes under attack, occasionally, the resources of the machine become exhausted creating a denial of service.  This, possibly, is not the aim of the attacker but a side effect of their Good Work.  Without an investigation that would find the attacks the application’s developer might ask for the hosting machine to be given more resources.  More of a resource, like RAM, would help the application to avoid the denial of service but would afford the attack more time in which to be successful.  And, of course, this would be expensive.  The increase in RAM could be used elsewhere and the machine would not always need the extra resource because the attacker will move on if the application is esoteric or reasonably well written.  It is easy to give extra RAM to a machine but it is harder to take it away.

These attacks are attempts to penetrate a system through a flaw in the application or operating system.  Most of the attacks we see are against popular applications: phpMyAdmin, WordPress, and their Windows equivalents.  As long as good practices, when developing a LAMP application, are used e.g. using prepared SQL statements to prevent SQL injection, the main application might be safer from attack than are the more popular well understood applications.  This situation is weakened when a utility like phpMyAdmin is used to provide functionality not yet present in the main application.

So, instead of adding more RAM to mitigate against an accidental denial of service and to protect well known applications as well as the main application, we could instead monitor for attacks and proactively protect the host machine accordingly.  This is where we might use Fail2Ban.

The Attack

As most attacks are against the application and most Internet connected application are web applications we are probably talking about Apache or NGINX for delivery of content.  We will spot attacks through the logs files, for example, error_log:

[Sun Nov 05 09:34:27 2017] [error] [client] File does not exist: /home/apache/public/htdocs/admin
[Sun Nov 05 09:34:27 2017] [error] [client] File does not exist: /home/apache/public/htdocs/admin
[Sun Nov 05 09:34:27 2017] [error] [client] File does not exist: /home/apache/public/htdocs/admin
[Sun Nov 05 09:34:27 2017] [error] [client] File does not exist: /home/apache/public/htdocs/apache-default
[Sun Nov 05 09:34:27 2017] [error] [client] File does not exist: /home/apache/public/htdocs/cpanelphpmyadmin
[Sun Nov 05 09:34:27 2017] [error] [client] File does not exist: /home/apache/public/htdocs/cpphpmyadmin
[Sun Nov 05 09:34:28 2017] [error] [client] File does not exist: /home/apache/public/htdocs/dbadmin
[Sun Nov 05 09:34:28 2017] [error] [client] File does not exist: /home/apache/public/htdocs/db

This shows one IP address (bad machine on the Internet) running through obvious URLs trying to find phpMyAdmin but failing (404).  It shows that there are many attempts in a short amount of time.  Fail2Ban could be set up to ban the bad machine for a period of time after the first three failures preventing the rest of the attempts draining the resource of the machine.  This log does not show actions that might exhaust a machine’s resources but if phpMyAdmin was found a series of tests could then be run against it and that might create a denial of service.

A Solution for this Attack

Fail2Ban is available to CentOS:

$ yum install fail2ban

The interesting aspects of this package for us are:


I’ll create this in /etc/fail2ban/jail.d/apache-fourofour.conf

enabled = true
port = http,https
filter = apache-fourofour
logpath = /home/apache/p*/logs/error_log
maxretry = 20
findtime = 120
bantime = 16400

The above isn’t the complete truth…because that would be telling!

And in /etc/fail2ban/filter.d/apache-fourofour.conf

failregex = [[]client <HOST>[]] File does not exist: *
ignoreregex = .*(robots.txt|favicon.ico|jpg|png)

The inspiration for this filter can be found here, created by Dominic Derdau.

So, a quick check to see if we get any hits (against a file we know has some):

fail2ban-regex home/apache/public/logs/error_log-20171112 /etc/fail2ban/filter.d/apache-fourofour.conf

reveals 184 hits.

Let’s enable the fail2ban service and start it.  This machine is CentOS 6:

# chkconfig fail2ban on
# service fail2ban start

and check that the firewall has Fail2Ban gaols set up:

# iptables -L -v -n
 0 0 f2b-apache-fourofour tcp -- * * multiport dports 80,443
Chain f2b-apache-fourofour (1 references)

Now, how to test?  A quick script that quits once it is blocked at the firewall:

while :
  echo "Attempt $n"
  let n=$n+1
  if [ $? -eq 7 ]
    echo 'Firewall block!'

The script above may surprise you.  It did surprise me.  I got many more attempts in before I was blocked.  This is because Apache, in this case, will serve pages as fast as it can but will write to the logs like it’s a hot lazy Sunday afternoon.  You can tune /etc/fail2ban/jail.d/apache-fourofour.conf to suit your needs.

Eeek, I’m in gaol:

Chain f2b-apache-fourofour (1 references)
 pkts bytes target prot opt in out source destination 
 17 1020 REJECT all -- * * reject-with icmp-port-unreachable 
 190 16313 RETURN all -- * *

So, this works.  Check that it works, too, after a reboot.  Fail2Ban should start running after iptables otherwise you’ll miss out on the gaol creation.

Well done you.

Posted in ITMS, Linux SysAdmin, Secuity | Tagged , , , , , | Leave a comment

Developing CampusM using Docker Containers

Back in December, I created a mobile app for Android and Apple using Ionic with AngularJS.  I did this using my desktop running GNU/Linux.  Traditionally, when a developer works with lots of technologies through her desktop new work can eventually step on the toes of other projects or impede the new work.  When I work with Windows I have to create a VM with a full windows install plus all of the tools.  To work with Ionic I created all of the tools locally and a VM with 100GB of disk space.  Therefore, if I want a simple life I will create a vm/container per project which means lots of VMs can quickly chew through disk space.  I have just created a Docker container (not-a-vm) so that I can start learning about and developing for CampusM.  I am am the point of writing the first line of code.  The Docker container takes up a whopping 1.1GB.

The following list is pretty close to what anyone else will need to do to copy this work.

On my desktop now, I just need a web browser and editor (Vi FTW).

A list:

  • desktop:
    • docker pull fedora
    • docker run -i -t -d fedora
    • docker ps
    • docker exec -i -t 25efc7b4714d bash
  • in container:
    • as root: dnf install npm
    • as root: npm install -g
    • as root: useradd -d /home/node -c Node node
  • desktop:
    • docker commit 6a6cf3686621 fedora/campusm
    • docker stop 6a6cf3686621
    • docker run -v /usr1/home/williams/Dev/CampusM/Projects:/home/node/Projects -p 5000:5000 -i -t -d fedora/campusm
    • docker ps
    • docker exec -i -t 0c6cac5cf04fa534b26ecb9aee74740c3e2724f6980a981ceed216b5e3129301 bash
  • container
    • as node
      • cd Projects
      • aek create
      • cd projectname
      • aek start
  • desktop

CampusM working through Docker

  • desktop
    • docker exec -i -t 0c6cac5cf04fa534b26ecb9aee74740c3e2724f6980a981ceed216b5e3129301 bash
    • create RunProject in the shared directory
      • #!/bin/bash
        su - node -c "cd /home/node/Projects/$1 && aek start"
  • container
    • as root
      • cp ~node/Projects/RunProject /usr/local/bin/
      • chmod +x /usr/local/bin/RunProject
  • desktop
    • now we don’t have to go in to the container to start the project
    • docker exec -t -i 2f85e2474912 /usr/local/bin/RunProject projectname

Well done you.

Posted in app, Development, Docker, ITMS, Linux SysAdmin, Virtual Machines | Tagged , , , , , , , | Leave a comment

Quick note: Monit-er FFMPEG : run ffmpeg as daemon

On CentOS 6, I just set up a script and monit to rerun ffmpeg if it crashes.  We’re using ffmpeg to push video from an IP camera to a CDN.

Screenshot from 2017-04-10 11-51-54FFMPEG

Install NUX repo in order to get FFMPEG:

$ rpm -Uvh

Note: the el6 + x86_64

$ yum install ffmpeg


Monit will monitor FFMPEG and restart it if FFMPEG crashes.

$ yum install monit


Please, don’t run this as root. Create a user “scriptcam”:

$ adduser -d /usr1/home/scriptcam -c 'Script Camera' scriptcam

Create script ScriptCam

In /usr/local/sbin/ScriptCam:

pid=`runuser -l scriptcam -c 'echo|/usr/bin/ffmpeg -v 0 -i rtsp://x.x.x.x/channels/1 -r 25 -vcodec copy -acodec copy -f flv rtmp://y.y.y.y/zzzzzzz-live/zzzzzzz01 >/dev/null 2>&1 & echo $!'`
echo $pid > $1

Create Init script for FFMPEG

Install to /etc/init.d/ffmpeg:

# ffmpeg Startup script for ffmpeg/ScriptCam
# chkconfig: - 85 15
# description: Push ScriptCam video to CDN
# processname: ffmpeg
# pidfile: /var/run/
# Provides : ffmpeg
# Required-Start : $local_fs $remote_fs $network $named
# Required-Stop : $local_fs $remote_fs $network
# Default-Start : 2 3 4 5
# Default-Stop : 0 1 6
# Short-Description : ffmpeg daemon
# Description : ffmpeg daemon

# Source function library.
. /etc/rc.d/init.d/functions


if [ "$(id -u)" != "0" ]; then
 echo "This script must be run as root"
 exit 1

start() {
 echo -n $"Starting $prog: "
 LANG=$HTTPD_LANG daemon --pidfile=${pidfile} /usr/local/sbin/FalconCam $OPTIONS
 [ $RETVAL = 0 ] && touch ${lockfile}
 return $RETVAL

stop() {
 echo -n $"Stopping $prog: "
 killproc -p ${pidfile} -d ${STOP_TIMEOUT} $prog
 [ $RETVAL = 0 ] && rm -f ${lockfile} ${pidfile}

case "$1" in
 exit 0
 exit 0
 exit 0
 echo "Usage: $0 {start|stop|restart}" 1>&2
 exit 1

Monitor with Monit

Use monit to monitor the ffmpeg process. Monit will restart the falcon cam if ffmpeg crashes.

Create /etc/monit.d/ffmpeg:

check process ffmpeg with pidfile /var/run/
      start program = "/etc/init.d/ffmpeg start" with timeout 60 seconds
      stop program = "/etc/init.d/ffmpeg stop"

At Boot

Configure monit to start at boot:

$ chkconfig monit on

Configure ffmpeg to start at boot:

$ chkconfig –add ffmpeg
$ chkconfig ffmpeg on


$ service ffmpeg restart # stop | start
$ service monit restart # stop | start

Check the monit web site (the user details are in /etc/monit.conf) :


Posted in Development, ITMS, Linux SysAdmin, university | Tagged , , , , , | Leave a comment

Ionic 2 : how to build three native mobile apps from one code base


I have just created an app using early versions of Ionic 2 (Apache Cordova with AngularJS).  The app has been accepted in to Google and Apple’s app stores.  Obviously, this means I am now Ionic 2 1337 and should write a guide on how to develop using the framework.  There are 750 lines of code in my first app, just to say… there are levels of 1337ness.

One of the reasons for writing up this up is that my colleagues should be able to use this and re-create the steps I took.  To make it interesting for me I am going to create a toy app that includes taking pictures.

Hat tips: of all the research (randomly dipping in to the Internet) I did, Josh Morony has been the greatest help through his blog.  Also, it would have taken even longer, health threateningly longer, to get the Windows tools working without Justin James‘s help.

We need tools

To develop three native apps I’m using three platforms: GNU/Linux, a physical Mac, and a Windows VM.  We could get away with just a Mac but I am way more productive with GNU/Linux.  We have not investigated building the app using a service in the cloud like Ionic’s.  I went through lots of iterations of building the tools that I can’t give detailed  and accurate instructions but hopefully through this I’ll show that it is possible to build Android, iOS and Windows Mobile apps.


  • for GNU/Linux building Android : essentially npm, git, Java SDK, Android SDK and a guide.
  • for Apple: npm, git, Java SDK, Android SDK, Xcode, an Apple Id and a guide.  For an introvert like me, I love the licence (without membership) and Id free world of GNU/Linux.  I can just get on and code.  If you don’t already have an Apple Id then nip over to an Apple store and get something for “free” so that when you create the Id you do not need to register a credit card.  I wrote that bit without swearing.  Set up an Apple Id using this method before you do anything else.  Otherwise, you could, like me, spend too much time trying to get things set up comfortably.  This step, for me, included phone calls!
  • Caveat : Windows hates me.  “Windows” seems apt because the OS seems to be a collection a small opportunities where the thing you have tried repeatedly suddenly works.  I’m sure colleagues who use Windows day in day out will have more luck.  The quickest way into Ionic and Windows might be this guide.  Justin James employs Chocolatey to batch install the tools he needs and because of him you can too.

We need magic

In no particular order these tricks might save your day:

  • I use this to build and deploy to a Windows Mobile set to developer mode and connected by USB to my Windows VM:
    ionic run --device -- --phone --arch=arm
  • Re-install plugins if things go awry:
    $ ionic plugin list
    On Linux, build a for loop from the output:
    $ for i in cordova-plugin-crosswalk-webview cordova-plugin-device 
    cordova-plugin-network-information cordova-plugin-splashscreen
    cordova-plugin-statusbar cordova-plugin-whitelist
    cordova-sqlite-storage cordova.plugins.diagnostic
    ionic-plugin-keyboard ;
     do   ionic plugin remove $i && ionic plugin add $i; done
  • Tidy up before release:
    ionic plugin rm cordova-plugin-console
  • package.json includes version numbers which can be fine tuned to get things working and this will update the current project:
    npm install
  • re-installing Ionic can help (as root):
    npm uninstall -g ionic && npm uninstall -g ionic
  • when you create a new project you get a .gitignore for free.  When you build on a different platform you need to check you have installed the necessary plugins and platform to build your app because these will not get added to your project
  • when we build on a new platform we will have lots missing when we pull from git.  The directory “www” was missing.  Ionic claimed that I was not building an Ionic project
  • also, for a first build on a new platform
    ionic setup sass
  • Icons and splash screens are fun.  For Android and iOS you can put an image 2048×2048 for the splash.png in ./resources and then run the following to build all the images the project needs
    ionic resources --splash && ionic resources --icon
  • Older Android versions have a poor web browser.  Install Crosswalk for consistency across versions:
    ionic plugin add cordova-plugin-crosswalk-webview
  • If you get Sass errors try:
    rm -rf node_modules
    npm install

Hello World

Somewhat riskily I’m upgrading to the official release of version 2 final.  This should be fine but I built my first app with rc3 then rc5.  There will be things to learn with the proper release.

Somewhere neat run:

ionic start IonicHelloWorld tabs --v2 --ts

This will create lots and lots of things, we are mostly interested in:

├── app
│   ├── app.component.ts
│   ├── app.html
│   ├── app.module.ts
│   ├── app.scss
│   └── main.ts
├── assets
│   └── icon
│   └── favicon.ico
├── declarations.d.ts
├── index.html
├── manifest.json
├── pages
│   ├── about
│   │   ├── about.html
│   │   ├── about.scss
│   │   └── about.ts
│   ├── contact
│   │   ├── contact.html
│   │   ├── contact.scss
│   │   └── contact.ts
│   ├── home
│   │   ├── home.html
│   │   ├── home.scss
│   │   └── home.ts
│   └── tabs
│   ├── tabs.html
│   └── tabs.ts
├── service-worker.js
└── theme
└── variables.scss

and resources, config.xml, package.json.

At this point we can already run our app in a web browser:

ionic serve

“ionic serve –lab” doesn’t work for me yet.

Let’s add a platform.  I’m on GNU/Linux, because it is my Happy Place, so I will add Android:

ionic platform add android

and now we can run our app in an emulator:

ionic run android

AndroidEmulatorThe are two ways to get the app on to a mobile device:

  • copy the android-debug.apk that was built in the last step and copy it on a device, then tell the device to trust apps found outside of the Playstore (Android app store) and install the app.  The signature for the app is the identification of the app.  New versions built in the same circumstances will replace the old version.  An app built with a different signature will appear as a separate app
  • via USB.  Set up the device so that it is in “developer mode”.  Connect it using a USB cable and check with “adb devices” that the computer can see it:
  • $ adb devices
    List of devices attached
    42eb627e device

    and then run “ionic run android” again.  Excited yet?  Maybe not, if you got a blank screen.  The plugin for loop from above fixed this for me

  • Google Chrome web browser has a trick we can use at this point: chrome://inspect will let us inspect and debug our running app.

Change some code

Looking at the tree structure above we can see that src/pages/home contains the home “tab”.  This will not be very exciting but if I go straight to trying to add camera functionality this blog entry is likely to crash and burn.  In the directory we have: home.html, home.scss, and home.ts.  We can change the text in the .html, the CSS in .scss and the Angular JS in the .ts file.  I spent a week learning version 1 of Ionic and I think version 2 will be better.  Let’s change the home tab… First of all run:

ionic serve

and navigate to http://localhost:8100/.  When we change a file the app will reload in the browser giving us the sense that what we change is what we see.  I use vi (Vim) in most situations because it is nearly always available (hey Windows, get with the programme!)  Edit home.html under src/pages/home/home.html.  Change “Welcome to Ionic!” to “My Little Camera App.” and save the code.  We should see the app reload in the browser and instantly display the change:

$ diff src/pages/home/home.html src/pages/home/home.html.orig 
< <h2>My Little Camera App.</h2>
> <h2>Welcome to Ionic!</h2>

Now, just for fun, let make the title green:

$ diff src/pages/home/home.scss src/pages/home/home.scss.orig
< h2 {
< color: green;
< }

Currently, I’m nervous of style changes.  When we imagine the range of devices and browsers, a style change might not be reflected the way we hope it would in every situation.

Time to get funky

Straight from the horse’s mouth, add the camera plugin:

ionic plugin add cordova-plugin-camera

This is where the fun begins.  Desktop web browsers do not have a native camera available to them.  We need to install our toy app on to a device to see the functionality.  I hope we can borrow a device from work and not compromise our own devices.

Next, let’s change “About” to be “Snap”.  This is fairly complex but essentially we are looking for instances in the file system and code that have “About” or “about” and changing to “Snap” and “snap”.  Change files:

$ find src -name '*about*'

and strings:

$ find src -type f| xargs grep -i about
src/declarations.d.ts: Declaration files are how the Typescript compiler knows about the type information(or shape) of an object.
src/declarations.d.ts: They're what make intellisense work and make Typescript know all about your code.
src/declarations.d.ts: To learn more about using third party libraries in an Ionic app, check out the docs here:
src/pages/tabs/tabs.html: <ion-tab [root]="tab2Root" tabTitle="About" tabIcon="information-circle"></ion-tab>
src/pages/tabs/tabs.ts:import { AboutPage } from '../about/about';
src/pages/tabs/tabs.ts: tab2Root: any = AboutPage;
src/pages/snap/snap.html: About
src/pages/snap/snap.scss:page-about {
src/pages/snap/snap.ts: selector: 'page-about',
src/pages/snap/snap.ts: templateUrl: 'about.html'
src/pages/snap/snap.ts:export class AboutPage {
src/app/app.module.ts:import { AboutPage } from '../pages/about/about';
src/app/app.module.ts: AboutPage,
src/app/app.module.ts: AboutPage,

I made those changes so quickly that the Ionic web server has become confused.  Rebuild the app “ionic build android“, restart the server “ionic serve“, and reload the web page.  Now, the icon “i” for Snap does not make sense.  Browse through the icons and choose a new one.  Make the following change to “tabs.html”:

$ diff src/pages/tabs/tabs.html src/pages/tabs/tabs.html.orig
< <ion-tab [root]="tab2Root" tabTitle="Snap" tabIcon="camera"></ion-tab>
> <ion-tab [root]="tab2Root" tabTitle="Snap" tabIcon="information-circle"></ion-tab>

Next, we need to tell the AngularJS to use the camera library, in “snap.ts”:

$ diff src/pages/snap/snap.ts src/pages/snap/snap.ts.orig
< import {Camera} from 'ionic-native';

Adding this will change the warning to the user if they were to install the app to their device.  The warning will say that the app wants access to the camera.

Skipping, because this is so easy, I’ll add a few more bit from the tutorial…

$ diff src/pages/snap/snap.ts src/pages/snap/snap.ts.orig 
< import {Camera} from 'ionic-native';
< public base64Image: string;
< }
< takePicture(){
< Camera.getPicture({
< destinationType: Camera.DestinationType.DATA_URL,
< targetWidth: 1000,
< targetHeight: 1000
< }).then((imageData) => {
< // imageData is a base64 encoded string
< this.base64Image = "data:image/jpeg;base64," + imageData;
< }, (err) => {
< console.log(err);
< });


$ diff src/pages/snap/snap.html src/pages/snap/snap.html.orig
< <ion-card>
< <ion-card-content>
< Hello World, this is my camera app
< <button (click)="takePicture()">Take a Picture</button>
< Latest Picture:
< <img [src]="base64Image" *ngIf="base64Image" />
< </ion-card-content>
< </ion-card>

We have linked, I like this bit, the event ‘click‘ and the function “takePicture()“.  Further down we can see:


The “*ngIf” is another bit of magic.  The image is displayed if “base64Imageis true.  Once we understand this we can do all sorts of things using the power of the evil side-effect.  If a variable is shared across the application a variable set in one tab can effect the magic on another tab.

Right, quick, build the app and deploy it to a device.  Plug the device in again test test “adb devices”.  Then run “ionic run android”.  If I have done a good job in explaining this, we should now have a little camera app running on Android.

Git it

As this is a toy app we won’t add this to TFS but we could do this…

Now we have something running it is probably a good time to add it to our Git repo (TFS).  We can develop on GNU/Linux and pull changes to Windows and Apple rather than go through the pain of developing on either of those platforms.  Ionic works well with git because a little code goes a long way.  A new feature can be added as code and push to git and make sense as a unit.  If we could automate the tools we might even see automatic building of the native apps ready for testing.

Another bite of the Apple

If we are lucky, we will have access to an polite but ancient (think hard drive and too little RAM) Mac Mini.  As above we should have all the tools including Xcode installed.

The slow Mac Mini I am using is headless and I use Remmina to VNC to the Mac Mini.  First, we copy the project on to the Mac because we have not set up git for this “toy” application.  In this case it can be useful to use the trick:

rm -rf node_modules
npm install

A good test is to run “ionic serve”.  Once that is working we can run:

ionic build ios

which is if completes successfully will create


which can be opened as a project in Xcode.  Attach an iDevice to the Mac and then set up Xcode to connect to it:

Mac Mini running Xcode

Mac Mini running Xcode

The device I am using is called TESTBOX21 which whould be in the drop down circled.  When we select it Xcode will do some jiggery pokery.  Click to edit the project and set “team” to an Apple Id.  Then click “play”.  Shortly, or longly for this Mac, we will be asked to allow the app to run on the iDevice.  On the iDevice go to Settings > General > Device Management.  Click on the Apple Id that you used, trust it and verify the app.  The app is install but we can click on “play” again.  Once again, we have a native version of our app but for iOS this time.

I’ve got that Windows feeling ♪ ♫ ♬

The toy app’s code is not in Git.  I’m stymied.  How do I get the code on to the Windows VM?  Apple has SSH.  The advice is to set up Samba on the GNU/Linux host.  Luckily, we have some Windows infrastructure and I can do two copies to get going…  I might take up knitting.  These copies are going very slowly…bigly slow.  I Ctrl-Ced that and put the code up to DMU’s open git server.

On the Windows VM:

git clone

Tell the project about Windows 10, edit using ‘code‘ config.xml:

$ diff config.xml config.xml.orig 
< <preference name="windows-target-version" value="10.0" />

Connect a Windows device to the Windows VM via USB.  Go in to the directory and :

npm install
ionic platform add windows
ionic plugin add cordova-plugin-camera

Finally, run the magic:

ionic run --device -- --phone --arch=arm

And there you have it.  One set of code running on three devices.

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Micro blogging server setup

On Fedora:

  • dnf install docker
  • systemctl start docker
  • docker run hello-world
  • docker pull turnkeylinux/gnusocial-14.0
  • CID=$(docker run -i -t –name social -p -p -p -p -p -d turnkeylinux/gnusocial-14.0)
  • CIP=$(docker inspect –format='{{.NetworkSettings.IPAddress}}’ $CID)
  • docker logs $CID | grep “Random initial root password”
  • ssh root@$CIP
  • cd /var/www/gnusocial
  • vi config.php
  • change $config[‘site’][‘server’] (e.g. ‘’) & $config[‘site’][‘name’]
  • change desktop host file to reflect $config[‘site’][‘server’]
  • web browse to

et voilà.

For every mistake I made, I ran:

docker stop social
docker rm $(docker ps -a -q) # deletes all containers!

and started again.  You could do this in less than 15 minutes!

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Protected: An app idea

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Test Pen

[iframe src=”″ width=”640″ height=”360″ frameborder=”0″]

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Raspberry Pi 3 and HostAPD throughput

Raspberry Pi 3 in a Pi2Go

Raspberry Pi 3 in a Pi2Go

The Raspberry Pi 3 has n-wireless (and bluetooth) onboard now.  I got this robot before Christmas “for my boys”.  I didn’t have much time with it before the holidays and couldn’t quite get it to work with a USB wifi dongle and USB storage (to hopefully store pictures from the camera.)

Anyway, I got the Raspberry Pi 3 (RPi3) yesterday and got hostapd working in a very short time using this RPI Wireless Hotspot.

I posted on Twitter that I got it working and got this tweet in reply:

So, here goes… I installed iperf on the RPi3 and locally on my laptop (Fedora 22 i7) with RT5370 USB dongle and Intel 7260 AC onboard.

Raspberry Pi 3 Aerial

Raspberry Pi 3 Aerial (picture from

I can’t find the reference on the web but someone asked if an external aerial could be fitted because his Pis are used in industrial applications and need to be housed in metal cases.  This got me to think that there might be a problem with a robot like mine when it rotates.

This is using the USB dongle on the laptop with the aerial facing away at two feet:

root@robotpi:/home/pi# iperf -s
[root@qedu ~]# iperf -c
Client connecting to, TCP port 5001
TCP window size: 85.0 KByte (default)
[ 3] local port 59856 connected with port 5001
[ ID] Interval Transfer Bandwidth
[ 3] 0.0-10.0 sec 24.5 MBytes 20.5 Mbits/sec

This is using the USB dongle on the laptop with the aerial facing towards it:

[root@qedu ~]# iperf -c
Client connecting to, TCP port 5001
TCP window size: 85.0 KByte (default)
[ 3] local port 60514 connected with port 5001
[ ID] Interval Transfer Bandwidth
[ 3] 0.0-10.1 sec 24.1 MBytes 20.1 Mbits/sec

From ten feet with the aerial facing away from the laptop:

[root@qedu ~]# iperf -c
Client connecting to, TCP port 5001
TCP window size: 85.0 KByte (default)
[ 3] local port 60792 connected with port 5001
[ ID] Interval Transfer Bandwidth
[ 3] 0.0-10.0 sec 24.0 MBytes 20.1 Mbits/sec

Now, with the AC wireless:

[root@qedu ~]# iperf -c
Client connecting to, TCP port 5001
TCP window size: 85.0 KByte (default)
[ 3] local port 56582 connected with port 5001
[ ID] Interval Transfer Bandwidth
[ 3] 0.0-10.3 sec 20.4 MBytes 16.7 Mbits/sec
[root@qedu ~]# iperf -c
Client connecting to, TCP port 5001
TCP window size: 85.0 KByte (default)
[ 3] local port 56600 connected with port 5001
[ ID] Interval Transfer Bandwidth
[ 3] 0.0-10.1 sec 21.9 MBytes 18.2 Mbits/sec

Ouch!  The USB wireless-n dongle is faster than the onboard wireless-AC.


Posted in Linux SysAdmin, Raspberry Pi | Tagged , , , , , | 1 Comment